In one aspect the present invention relates to aqueous gelled explosive compositions containing water-in-oil emulsion explosive compositions as sensitizers. In another aspect, this invention relates to the use of water-in-oil explosive emulsions as a substitute for sensitizing agents such as high explosives and metallic fuels in aqueous gelled explosive compositions. In still another aspect this invention relates to a process for preparing a sensitive aqueous gel explosive composition employing water-in-oil explosive emulsions as sensitizing agents.
Aqueous slurry blasting agents have become increasingly more important in the blasting industry due to their ease of preparation, water resistance and ease of handling. The addition of a gelling agent to form aqueous gel explosive compositions has become increasingly popular within the explosives industry because of the water resistance and tamping properties of such compositions. Generally, gelled explosive compositions are composed of oxidizers, water, fuels, sensitizing agents and bulking and gelling agents. By controlling the amount of gelling agent present in the composition, gelled explosives can take the form of a flowable fluid or a relatively stiff gelled composition which can be packaged in a variety of containers. It has been recognized in the past that gelled explosive compositions must contain a sensitizing agent in order to have acceptable strength and detonation properties. In the past high explosives or particulized metallic agents have been employed in order to sensitize the oxidizer-water mixture. However, use of pre-manufactured high explosives, such as TNT for example, presents a safety hazard in the handling, manufacture and transportation of the explosive gel compositions. Further, sensitizing agents which have been employed in the past are relatively expensive.
A separate and distinct type of explosive compositions are water-in-oil emulsion type blasting agents. Basically, these blasting agents contain an aqueous solution of inorganic oxidizer salt which is emulsified as the dispersed phase within a continuous carbonaceous fuel phase. Water-in-oil emulsions also contain a uniformly distributed gaseous component as a sensitizer. Water-in-oil emulsion type blasting agents were first disclosed by Bluhm in U.S. Pat. No. 3,447,978. As is the case with gelled explosive compositions, water-in-oil emulsion explosives have been widely accepted by the explosive industries because of their water resistance and superior handling qualities. However, there is a marked distinction between water-in-oil type emulsion blasting agents and the aqueous gelled explosive compositions described above. Gelled explosive compositions basically comprise an aqueous solution of oxidizers, fuels and sensitizing agents which has been gelled with one of a variety of aqueous gelling agents such as guar gum and a suitable crosslinker for example. In contrast, water-in-oil emulsion explosives are comprised of two distinct phases, the carbonaceous oil being the continuous phase and the aqueous solution of oxidizing agents being the discontinuous phase of the emulsion with a dispersed gaseous component distributed throughout the emulsion.
Because of the rapid and wide acceptance of gelled explosive compositions the development of relatively sensitive gelled explosive compositions which do not employ relatively expensive or hazardous materials, such as pre-manufactured high explosives, is desirable. In the past various attempts have been made to eliminate the need for pre-manufactured high explosive sensitizing agents. For example, U.S. Pat. No. 3,431,155 discloses the use of methyl amine nitrate as a sensitizer for aqueous gel explosives. However, this is a relatively expensive ingredient and does not completely resolve the safety problems present when high explosive sensitizers are used. Another sensitizing agent for aqueous gel explosive compositions is disclosed in U.S. Pat. No. 3,923,565. That patent discloses that sodium dodecyldiphenyl ether disulphonate may be used as a sensitizing agent in aqueous gel explosives. However, it appears that the final explosive compositions of that reference must have a density lower than about 1.15 grams per cubic centimeter in order to obtain maximum useful detonation characteristics. Therefore, there if a continuing need in the explosive industry for an aqueous gel explosive composition which can be sensitized without the use of relatively expensive or dangerous sensitizing agents and which can be formulated so as to have a range of useful densities.